RT Journal Article
T1 Photochemical Oxidation of Thioketones by Singlet MolecularOxygen Revisited: Insights into Photoproducts, Kinetics, andReaction Mechanism
A1 Sánchez Arroyo, Antonio José
A1 Pardo Botero, Zulay D.
A1 Moreno Jiménez, Florencio
A1 Herrera Fernández, Antonio
A1 Martín, Nazario
A1 García Fresnadillo, David
AB Photosensitized oxidation of trimethyl[2.2.1]-bicycloheptane thioketones by 1 O2 can yield more photoproducts than exclusively ketones and sulfines. Moreover, the ketone/sulfine ratio can be reversed when protic conditions and high thioketone concentrations are used, conversely to earlier results reporting ketones as the main photoproducts. A new mechanistic proposal for sulfine formation is suggested following intermolecular oxygen transfer from a peroxythiocarbonyl intermediate to a second thioketone molecule. Reaction quantum yields (10−5−10−2) depend on the reaction conditions and time. Sulfine production reaches a maximum at short irradiation times, whereas decomposition to the corresponding ketone is observed at long reaction times. When the thioketone substrate has a hydrogen atom at the α position a peroxyvinylsulfenic acid intermediate can be formed by proton transfer. Reaction of this intermediate with another thioketone molecule can yield more sulfine and its tautomeric vinylsulfenic acid, which dimerizes in situ to the thiosulfinate. The hydroperoxyl group of the peroxyvinylsulfenic acid can also rearrange to the α position, and by reaction with the starting thioketone, α-hydroxy thioketone and additional sulfine can be formed, while dehydration yields the α-oxo thioketone. In situ [2 + 2] and [4 + 2] self-cycloaddition of the α-oxo thioketone yields significant amounts of the corresponding adducts at prolonged irradiation times.
PB ACS
SN 0022-3263 (Print) 1520-6904(Online)
YR 2015
FD 2015-09-30
LK https://hdl.handle.net/20.500.14352/23907
UL https://hdl.handle.net/20.500.14352/23907
LA eng
NO Received: July 23, 2015; Published: September 30, 2015
NO Ministerio de Ciencia e Innovación (MICINN)
NO Universidad Complutense de Madrid
DS Docta Complutense
RD 6 oct 2024